Quantifying Methane Influx from Sewer into Wastewater Treatment Processes
Yijun Yin, Xiang Qi, Lan Gao, Xi Lu, Xufei Yang, Kang Xiao, Yanchen Liu, Yong Qiu, Xia Huang, Peng Liang
Abstract
Wastewater treatment contributes substantially to methane (CH 4 ) emissions, yet monitoring and tracing face challenges because the treatment processes are often treated as a “black box”. Particularly, despite growing interest, the amount of CH 4 carryover and influx from the sewer and its impacts on overall emissions remain unclear. This study quantified CH 4 emissions from six wastewater treatment plants (WWTPs) across China, utilizing existing multizonal odor control systems, with a focus on Beijing and Guiyang WWTPs. In the Beijing WWTP, almost 90% of CH 4 emissions from the wastewater treatment process were conveyed through sewer pipes, affecting emissions even in the aerobic zone of biological treatment. In the Guiyang WWTP, where most CH 4 from the sewer was released at the inlet well, a 24 h online monitoring revealed CH 4 fluctuations linked to neighborhood water consumption and a strong correlation to influent COD inputs. CH 4 emission factors monitored in six WWTPs range from 1.5 to 13.4 gCH 4 /kgCOD rem, higher than those observed in previous studies using A 2 O technology. This underscores the importance of considering CH 4 influx from sewer systems to avoid underestimation. The odor control system in WWTPs demonstrates its potential as a cost-effective approach for tracing, monitoring, and mitigating CH 4 .